SHANGHAI (Reuters) - Fake invoicing inflated China's official import and export totals by $75 billion in the first four months of 2013, local media reported on Friday, citing an internal review by China's commerce ministry.

An alternate estimate found that actual year-on-year export growth for January to April was only around 7 percent, while import growth was about 6 percent, the 21st Century Business Herald reported, citing an unidentified source and an internal commerce ministry document.

The second estimate was based on excluding data from the port of Shenzhen, where much of the fraud is suspected to have occurred.

Evidence has been growing in recent weeks that the world's second-largest economy is fast losing momentum, but suspect trade data has clouded the picture for global investors.

China's customs administration officially reported export growth of 17.4 percent in the first four months of the year, while imports officially grew 10.6 percent.

But analysts widely suspected that the data was distorted by inflated invoices used to circumvent China's strict capital controls and profit from appreciation of the Chinese currency.

The sharp drop occurred after China's customs agency promised to probe inconsistencies between China's export data and data on Chinese imports published by trading partners such as Hong Kong.

China's foreign exchange regulator also issued new rules in early May strengthening oversight of trade invoicing.

The $75 billion estimate was based on an examination of logistics data from China's special customs regulation zones. Such zones are the site of China's bonded warehouses, where analysts suspect much of the fake invoicing occurred.

Bonded warehouses are physically located inside China, but domestically-produced goods stored there have already cleared customs and are therefore counted as exports.

Imports and exports to and from the special regulation zones increased by 130 percent year-on-year in January through April, compared to only 19.1 percent in May, after tighter oversight began.

Assuming the true growth rate for January through April was similar to the reported growth rate in May produces an estimate of $75 billion in fake trade. That compares to official data showing combined imports and exports totaling $1.33 trillion in the same period.